Image of the Casius Quadrangle (MC-6). The southwest area contains Nilosyrtis Mensae (faults, measa and buttes); the rest of the area is mostly smooth plains.

The Casius quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the north central portion of Mars’ eastern hemisphere and covers 60° to 120° east longitude (240° to 300° west longitude) and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Casius quadrangle is also referred to as MC-6 (Mars Chart-6).[1] Casius quadrangle contains part of Utopia Planitia and a small part of Terra Sabaea. The southern and northern borders of the Casius quadrangle are approximately 3,065 km and 1,500 km wide, respectively. The north to south distance is about 2,050 km (slightly less than the length of Greenland).[2] The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area.[3]

Polygonal, patterned ground is quite common in some regions of Mars, especially in scalloped topography.[7][8] It is commonly believed to be caused by the sublimation of ice from the ground. Sublimation is the direct change of solid ice to a gas. This is similar to what happens to dry ice on the Earth. Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer that fell from the sky when the climate was different.[9] Polygonal ground is generally divided into two kinds: high center and low center. The middle of a high center polygon is 10 meters across and its troughs are 2–3 meters wide. Low center polygons are 5–10 meters across and the boundary ridges are 3–4 meters wide.

Low center polygons, shown with arrows, as seen by HiRISE under HiWish program Image was enlarged with HiView.

High center polygons, shown with arrows, as seen by HiRISE under HiWish program. Image enlarged with HiView.

Scalloped terrain labeled with both low center polygons and high center polygons, as seen by HiRISE under HiWish program Image enlarged with HiView.

High and low center polygons, as seen by HiRISE under HiWish program Loacation is Casius quadrangle. Image enlarged with HiView.

Ring Mold Craters

Ring Mold Craters look like the ring molds used in baking. They are believed to be caused by an impact into ice. The ice is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape."[10][11][12] They may be an easy way for future colonists of Mars to find water ice.

CTX context image for next image taken with HiRISE. Box indicates image footprint of following image.

Possible ring mold crater, as seen by HiRISE under the HiWish program. Crater shape is due to impact into ice.

Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Concentric crater fill is when the floor of a crater is mostly covered with a large number of parallel ridges.[13] They are thought to result from a glacial type of movement.[14][15] Sometimes boulders are found on concentric crater fill; it is believed they fell off crater wall, and then were transported away from the wall with the movement of the glacier.[16][17]Erratics on Earth were carried by similar means. Based on accurate topography measures of height at different points in these craters and calculations of how deep the craters should be based on their diameters, it is thought that the craters are 80% filled with mostly ice. That is, they hold hundreds of meters of material that probably consists of ice with a few tens of meters of surface debris.[18] The ice accumulated in the crater from snowfall in previous climates.[19]

High resolution pictures taken with HiRISE reveal that some of the surfaces of concentric crater fill are covered with strange patterns called closed-cell and open-cell brain terrain. The terrain resembles a human brain. It is believed to be caused by cracks in the surface accumulating dust and other debris, together with ice sublimating from some of the surfaces.[20]

Wide-view of concentric crater fill, as seen by HiRISE.

Concentric Crater Fill Close-up of near the top of previous image, as seen by HiRISE. The surface debris covers water ice.

Well-developed hollows, as seen by HiRISE under the HiWish program. Location is the Casius quadrangle. Note: this is an enlargement of the previous image that was taken by CTX.

Close-up that shows cracks containing pits on the floor of a crater containing concentric crater fill, as seen by HiRISE under HiWish program.

Close-up that shows cracks containing pits on the floor of a crater, as seen by HiRISE under HiWish program. Cracks may start as a line of pits that enlarge, then join.

Nilosyrtis

Nilosyrtis runs from about 280 to 304 degrees west longitude, so like several other features, it sits in more than one quadrangle. Part of Nilosyrtis is in the Ismenius Lacus quadrangle, the rest is in Casius quadrangle.

Nilosyrtis Channel.JPG

Channel in Nilosyrtis that was formed when a lake in a 45-mile-wide crater drained, as seen by THEMIS.

Niolsyrtis Landing Site.JPG

Landing Site in Nilosyrtis, as seen by THEMIS. Site is flat and contains water-altered clay minerals.

Climate change caused ice-rich features

Many features on Mars, including many in Casius quadrangle, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees[21][22] Large changes in the tilt explains many ice-rich features on Mars.

Studies have shown that when the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles.[23] Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Calculations suggest this material will concentrate in the mid-latitudes.[24][25] General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found.[26] When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust.[27][27][28] The lag deposit caps the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind.[29] Note, that the smooth surface mantle layer probably represents only relative recent material.

Mars Science Laboratory

Nilosyrtis is one of the sites proposed as a landing site for the Mars Science Laboratory. However, it did not make the final cut. It was in the top 7, but not in the top 4. The aim of the Mars Science Laboratory is to search for signs of ancient life. It is hoped that a later mission could then return samples from sites identified as probably containing remains of life. To safely bring the craft down, a 12-mile-wide, smooth, flat circle is needed. Geologists hope to examine places where water once ponded.[30] They would like to examine sediment layers.

Layers

Many places on Mars show rocks arranged in layers. A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.[31] Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.[32] Layers may be formed by groundwater rising up depositing minerals and cementing sediments. The hardned layers are consequently more protected from erosion. This process may occur instead of layers forming under lakes.

Layers in Monument Valley. These are accepted as being formed, at least in part, by water deposition. Since Mars contains similar layers, water remains as a major cause of layering on Mars.

Gullies

Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendriticalcove at its head, a fan-shapedapron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape.[33] They are believed to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes which themselves considered to be quite young. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research. As soon as gullies were discovered,[33] researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found.[34] Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water.[35][36][37] With continued observations many more changes were found in Gasa Crater and others.[38] With more repeated observations, more and more changes have been found; since the changes occur in the winter and spring, experts are tending to believe that gullies were formed from dry ice. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon-dioxide frost and temperatures that would not have allowed for liquid water. When dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes.[39][40][41] In some years frost, perhaps as thick as 1 meter.

Pedestal crater, as seen by HiRISE under HiWish program The ejecta is not symmetrical around crater because the asteroid came at a low angle out of the North East. The ejecta protected the underlying material from erosion; hence the crater looks elevated.

Close-up of East side (right side) of previous image of pedestal crater showing polygons on lobe. Since the margin of the crater has lobes and polygons, it is believed there is ice under the protective top. Picture taken with HiRISE under HiWish program. Note: this is an enlargement of the previous image.

Pedestal crater, as seen by HiRISE under HiWish program Dark lines are dust devil tracks.

Pedestal crater with boulders along rim. Such craters are called "halo craters."[42] Picture taken with HiRISE under HiWish program.

Close view of boulders on lower left of crater rim Box is the size of a football field, so boulders are roughly the size of cars or small houses. Picture taken with HiRISE under HiWish program.

Close view of boulders along crater rim Boulders are roughly the size of cars or small houses. Picture taken with HiRISE under HiWish program.

Cones

Some locations on Mars display a large number of cones. Many have pits at the top. There have been a number of ideas put forth as to their origins. Some are in the Casius quadrangle like the ones below.

ESP 043791 2120conesbands.jpg

Cones along with a band of material of unknown origin. Picture taken with HiRISE under HiWish program.

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Cones along with a band of material of unknown origin. Picture taken with HiRISE under HiWish program. Arrows point to the edge of bands.

Linear Ridge Networks

Linear ridge networks are found in various places on Mars in and around craters.[43] Ridges often appear as mostly straight segments that intersect in a lattice-like manner. They are hundreds of meters long, tens of meters high, and several meters wide. It is thought that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids cemented the structures. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind. Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation.[44][45][46] Water here could have supported

Network of ridges, as seen by HiRISE under HiWish program Ridges may be formed in various ways.

Color, close-up of ridges seen in previous image, as seen by HiRISE under HiWish program

More ridges from the same place as the previous two images, as seen by HiRISE under HiWish program

43845 2130ridgesclose.jpg

Ridge network close-up, as seen by HiRISE under HiWish program

Linear ridge network, as seen by HiRISE under HiWish program

Close-up and color image of previous image of linear ridge network, as seen by HiRISe under HiWish program

36869 2105ridgesclose.jpg

Close-up of ridges, as seen by HiRISE under HiWish program

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Close-up of ridges, as seen by HiRISE under HiWish program

More linear ridge networks, as seen by HiRISE under HiWish program

These ridges may be dikes or joints formed as a consequence of a crater impact. as seen by HiRISE under the HiWish program.

ESP 045124 2135ridges.jpg

Ridges, as seen by HiRISE under HiWish program

Glaciers

Old glaciers are found in many places on Mars. Some are associated with gullies.

Glacier on a crater floor, as seen by HiRISE under HiWish program The cracks in the glacier may be crevasses. There is also a gully system on the crater wall.

Scalloped terrain

Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation (direct transition of a material from the solid to the gas phase with no intermediate liquid stage). This process may still be happening at present.[47] This topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.[48]

ESP 044042 2240scalops.jpg

Scalloped terrain, as seen by HiRISE under HiWish program

Scalloped ground, as seen by HiRISE under HiWish program.

Close-up of scalloped ground, as seen by HiRISE under HiWish program. Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.

Close-up of scalloped ground, as seen by HiRISE under HiWish program. Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.

44042 2240scallopedterrain.jpg

Wide view of scalloped terrain showing depressions merging, as seen by HiRISE under HiWish program

Craters

Adamas Labyrinthus Crater.JPG

Crater in the Adamas Labyrinthus Region, as seen by HiRISE. The original image shows many interesting details.

Bacolor Crater Ejecta, as seen by HiRISE. Scale bar is 1000 meters long.

Dunes and old glaciers in Renaudot Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Arrows point to old glaciers along the crater wall. Note: this is an enlargement of the previous image.

Other Views from Casius

Another view of surface of Nilosyrtis Mensae, as seen by HiRISE, under the HiWish program.

24473pits.jpg

Pits that seem to be forming cracks, as seen by HiRISE under HiWish program.

Holes and hollows on crater floor, as seen by HiRISE under HiWIsh program.

Dust devil tracks, as seen by HiRISE under HiWish program. Location is Casius quadrangle.

ESP 045335 2155ribs.jpg

Ribbed terrain, as seen by HiRISE under HiWish program

Other Mars quadrangles

The thirty cartographic quadrangles of Mars, defined by the United States Geological Survey.[49][50] The quadrangles are numbered with the prefix "MC" for "Mars Chart."[51] Click on a quadrangle name link and you will be taken to the corresponding article. North is at the top; Lua error in Module:Coordinates at line 668: callParserFunction: function "#coordinates" was not found. is at the far left on the equator. The map images were taken by the Mars Global Surveyor.